Two-piece muffler comprising external shell and concentric deformed inner tube



Oct. 5, 1965 J fi 3,209,859 TWO-PIECE MUFFLER COMPRISING EXTERNAL SHELL AND CONCENTRIC DEFORMED INNER TUBE This application is a continuation of the applicants copending application, Serial No. 153,176, filed November 1'7, 1961, now abandoned.

This invention relates to mufilers and in particular to one of simplified construction for use with lawn mower engines and the like.

The muffier of the present invention is characterized by its simplicity of construction and ease of manufacturing which provides significant economic advantages to both the manufacturer and customer while affording an effective sound muflling device.

The main objects of the invention are to provide an effective sound muffiing device with simplified construction all-owing it to be inexpensively produced; to provide a mufiler shell having an end portion with threads integrally formed thereon for securing the muffler to the engine; to provide a mufller perforated center tube which is pinched intermediate its ends to provide an outlet into an expansion chamber and an inlet into a constricted gas outlet; and to provide a two-piece mufiler which is adapted for automatic machine formation and assembly.

Further objects, advantages and novel features of the invention will become apparent from the following description taken in conjunction with the drawings wherein:

FIGURE 1 is a longitudinal sectional view of the muffler;

FIGURE 2 is a cross-sectional view of the mufller taken along the line 22 of FIGURE 1; and

FIGURE 3 is a cross-sectional view of the mufller taken along the line 3-3 of FIGURE 1.

In the drawing, the muffler 10 comprises a shell 12 and a center tube 14. The shell is reduced in diameter at its inlet end 16 and threads, preferably pipe threads, 18 are formed in the outer surface thereof for securing the mufiler to an engine 20 to connect the inlet end of the muffler with the exhaust passage 22 of the engine. The center tube 14 is provided with perforations 24 and a pinched portion 26 which separates the tube into an inlet portion 28 and an outlet portion 30. The inlet end 32 and the outlet end 34 of the tube are respectively tightly frictionally engaged by the inlet end 16 and the outlet end 36 of the shell to provide an expansion chamber 38 into which the discharge gas puffs from the engine 20 are disseminated by the perforations 24 in the inlet portion 28 of the tube, and from which the expanded gas then flows through the perforations 24 in the outlet end of the tube to be emitted from the mufiler. This flow path results in a significant decrease in the energy of the exhaust gas puffs and a reduction of the noise caused thereby.

United States Patent 3,209,859 Patented Oct. 5, 1965 In the manufacture of the muffler the inlet and outlet ends 16 of shell 12 are simultaneously swaged by reducing dies which causes the end 16 to become thickened so that the threads 18 may be conveniently rolled or otherwise formed therein. Simultaneously with this reduction of the ends of the shell, the ends of the center tube 14 will be engaged by the shell and also reduced in diameter as indicated in FIG. 1. The tube is provided with the pinched portion 26 prior to its insertion in the shell 12. It is readily seen that the manufacture of this mufiler can be made by completely automatic machinery provided with hopper feeds for the shell and inner tube 14.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claim.

What is claimed is:

A two-piece gas mufller comprising a tubular external shell having a gas inlet at one end and a gas outlet at the other end, a perforate gas flow tube extending coaxially within said shell and extending between and connecting said inlet and outlet, the space between the outer periphery of said tube and the inner periphery of said shell forming a chamber communicating with the interior of said tube through the perforations in the wall thereof, said tube being formed with a first side portion intermediate the opposite ends thereof which projects radially inwardly to a position substantially intermediate the opposite sides of said tube and a second side portion axially aligned with said first portion and projecting radially inwardly to a position engaging the radially innermost section of said first side portion, whereby to provide a gas-tight partition between the opposite ends of said tube and to divide said tube into an inlet section and an outlet section, the perforations in said tube communicating said inlet and said outlet sections with said chamber, said chamber comprising an expansion chamber and a connecting path for gas to flow from the inlet section of said tube to said outlet section of said tube.

References Cited by the Examiner UNITED STATES PATENTS 577,852 3/97 Hain 181-59 1,318,210 10/19 Boiteaux. 1,949,074 2/ 34 Gunn. 2,115,128 4/38 Starkweather et al. 181-57 2,416,452 2/47 Marx 18149 2,548,965 4/51 Gaugler 18155 X 2,962,110 11/60 Depman 18l56 X 3,009,530 11/61 Cocklin 18161 X FOREIGN PATENTS 25,897 1908 Great Britain. 280,719 11/ 27 Great Britain.

LEO SMILOW, Primary Examiner. 

